All these terms have been deemed unparliamentary language in Canada; use of them, and 102 other specified pieces of verbal abuse, may result in penalties levied by the Speaker of the House of Commons upon members of Parliament.

To this list we must now add climate Barbie, a phrase so steeped in vileness that both the offending MP and the leader of the Opposition were forced to apologize.

To suggest that the federal minister of the Environment was possessed of no more scientific insight than a child’s toy was, indeed, a low blow. But that minister, Catherine McKenna, has also been disrespectful in her speech. She has referred to some of her opponents as climate-change deniers, a far more insidious charge and one much more corrosive of democratic values. By using the word ‘denier,’ she’s engaging in several kinds of linguistic nastiness.

First, those who are contrarians or skeptics about the climate consensus do not deny that long-term weather patterns are subject to change, so McKenna, who is a smart lawyer and surely knows this, seems to be engaging in a deliberate misrepresentation of the views of Canadians who disagree with her.

A good rule for public debate is to state your opponent’s arguments as clearly as possible, in a way that the person who holds this position would accept as fair.

Politicians seldom do this but it’s not unfair to hold a federal minister to this standard, especially when she has complained about being slurred.

But what’s worse is that the term denier seems slyly meant to associate skeptics with genocide or insanity. To be a Holocaust denier is to contradict the evidence of mass murder by Nazis. And so, by insinuation, to be doubtful of the effects of atmospheric carbon dioxide is to be ‘climate Hitler.’

It’s a neat linguistic trick and surely not accidental.

Furthermore, to be in denial is to maintain an alternate reality, at odds with the facts. ‘In denial’ is a phrase used in psychiatry to describe an irrationality, a defence mechanism to guard the psyche against disturbing facts and ideas. So if one states that temperatures today are no higher than during the Medieval Warm Period, do we suffer from ‘climate insanity’?

The debate about the future of our climate is enormously important, with billions of dollars and (perhaps) billions of lives at issue.

Name calling doesn’t help a democracy come to the right conclusions. Attributing bad motives to an opponent doesn’t make the issues any clearer. Banning opposing viewpoints from journals or academic posts only engenders ill will.

This topic is too important for cheap shots from ministers or their opposition.

Gerry Bowler is a Winnipeg historian and a senior fellow at the think-tank Frontier Centre for Public Policy.